Austin - The third package to explode in Austin this month, severely injuring a 75-year-old woman, was addressed to a different home nearby, according to people familiar with the investigation - adding a wrinkle to investigators' efforts to identify who is responsible for leaving sophisticated bombs on the doorsteps of unsuspecting residents.
The FBI and police have not identified a suspect or motive behind the attacks, and the clues revealed publicly have only deepened the mystery.
The two people killed in the explosions, a 39-year-old construction worker and a 17-year-old high school student, had relatives who were good friends and prominent members of Austin's African-American community, leading family members to speculate that they were targeted, perhaps in part because of their race.
But a victim in the third attack, the 75-year-old Hispanic woman, had no apparent connections to the other two. The woman, Esperanza Herrera, was visiting her mother's house, and people familiar with the case said the package she picked up was addressed to a different home.
Investigators have been poring over the victims' backgrounds and the construction of the bombs, hoping to find a clue that might lead them to the person or people responsible. The FBI sent behavioural profilers from Quantico, Virginia, as well as bomb technicians and evidence teams, said Christopher Combs, special agent in charge of the bureau's San Antonio office.
Police warned Austin residents to be wary when approaching packages left at their doorsteps and said they had received 265 calls about suspicious packages between Monday and Tuesday afternoon. None were deemed to be dangerous or related to the investigation.
Austin Police Chief Brian Manley said Tuesday that police were not ruling anything out in the case, including that the attacks could have been motivated by racial hatred or terrorism. He said that whoever is behind the attacks has been able to construct and deliver deadly bombs without setting them off at any point in that process, which shows some level of bombmaking prowess.
"When the victims have picked these packages up, they have at that point exploded," Manley said during an appearance Tuesday morning on KXAN, an Austin television station. "There's a certain level of skill and sophistication that whoever is doing this has."
He said the city would offer a $50 000 reward for information leading to an arrest in the investigation, on top of the $15 000 reward announced by Gov. Greg Abbott, R, a day earlier. "We need to put a stop to this before anybody else in our community is seriously injured or killed," Manley said.
The bombings come at a time when Austin is deluged by tens of thousands of visitors for the South by Southwest festival. Officials have said they do not see any connection between the bombings and the festival, although for some, their reassurances are hard to stomach.
After the first bomb exploded on March 2, killing 39-year-old Anthony Stephan House, police said it appeared to be an isolated incident with no continuing threat to the community. Then, on Monday, two more bombs went off.
House, a construction worker, was married with an 8-year-old daughter. His stepfather, Freddie Dixon, said Monday that the girl was inside the home when the explosion occurred. He said he was disappointed with how police had initially characterized it.
"Now, all of a sudden, they got to back up," Dixon said in an interview Monday.
During a Tuesday news conference, Manley said that law enforcement's working theory after House's death was that the incident was related to a raid police had conducted three days earlier on an apparent drug stash house on the street where House lived.
He said House's home was similar in color to the house that was raided and had similar vehicles parked outside. Investigators believed the bomb there might have been a "retaliatory act" for the police raid and that the presumed retaliator had gotten the wrong house, Manley said.
Dixon said he was good friends with Norman Mason, the grandfather of the 17-year-old killed in the first explosion early Monday morning. Mason's grandson, Draylen Mason, was a senior at East Austin College Prep, where he was well known for his love of music. His mother was also injured in the blast, and Manley said Tuesday that she was in stable condition.
"He was amazing, so passionate and very well rounded," said junior Eli Hernandez, 17, who considered Draylen Mason something of a role model. "Everyone could see he had a bright future with music."
School custodian Dennis Govea said Mason played stand-up bass and was in a mariachi band. In photos from the school's 2015-2016 yearbook, Mason is pictured taking part in the Austin Soundwaves, a Hispanic Alliance music education program; on a school field trip to Thailand; and grinning in his class photo. In 10th grade, Mason and two other classmates were named "most likely to be famous."
"A lot of kids are going to be hurting," Govea said. "We're sure going to miss him here."
Doug Dempster, dean of the University of Texas at Austin's College of Fine Arts, said in a written statement that Mason was "the very most remarkable talent in a most remarkable youth orchestra program," referring to Austin Soundwaves. He said he had watched Mason blossom for years and "knew he had the chops to study music in college."
Dempster said he expected Mason to attend the university in the fall.
"He was every inch a musician," he said in a statement. "He carried himself with a kind of quiet maturity that belied his youth. At Sound Waves performances one could often see him leaning in to lead and coach younger and more tentative players. His gentle confidence seemed to come from a conviction that hard work and talent was going to work for him. It did."
Dixon said his stepson did not know Mason, but he said he couldn't help but wonder whether his own connection with Mason's grandfather was somehow important. He said he was once the pastor at Wesley United Methodist Church, which Norman Mason attended, and the two were longtime friends and fraternity brothers.
"It's not just coincidental," Dixon said. "Somebody's done their homework on both of us, and they knew what they were doing."
Asked about his theory of the crime Monday, Dixon said: "My diagnosis: Number one, I think it's a hate crime. Number two, somebody's got some kind of vendetta here."
Of the bomb that injured Herrera, he said, "Is she a diversion to throw this off and lead to something else?"
The Washington Post could not immediately learn whether the packages that killed Mason and House bore any markings, such as the address on the one that injured Herrera. Police were still responding to the bomb that killed Mason when another one went off at the home Herrera was visiting, authorities have said.
Herrera remained in critical condition with life-threatening injuries Tuesday, Manley said. Relatives and neighbors said she had been visiting her mother, Maria Moreno, and often stayed in her home overnight to help provide care. The significance of the package left at that home bearing the wrong address was not immediately clear.
Jesse Barba, 77, a neighbour of Herrera's, said he rarely saw Herrera, because "she was always helping out with her mother."
"She used to come by and pick roses from my yard to take to her mother," Barba said. "She loved them so much I gave her a piece of the bush."
The site of the blast was still roped off with police tape on both ends of Galindo Street on Tuesday, and police were not letting anyone but residents pass through. Television trucks and reporters amassed at the street's west entrance, where an FBI truck and an Austin Police Department cruiser sat.
Community organisers said they planned an event Friday night to discuss what has been happening and potentially talk about raising money for more cameras in east Austin.
"People are angry and afraid," Fatima Mann, an organiser, said Tuesday. "I refuse for people to have to go through life afraid because they don't know if they'll be next. This is an issue that should have been dealt with when the first explosion went off."