DA Provincial Chairperson Haniff Hoosen confirmed the incident. He said Baker was the party's representative on Parliaments Water and Sanitation committee who were in the province at the request of the provincial leadership to conduct an oversight visit into the water crisis in the Ugu District Municipality.
She had flown in from Cape Town on Thursday night, visited sites down the South Coast and in the late afternoon stopped in Park Rynie to visit DA activists.
She had parked her car and was crossing the road at a traffic intersection when the truck hit her, said Hoosen. He said it was believed the truck was speeding.
Baker, who lives in Mpumalanga, is from Durban and her parents still live in Durban.
"Her heart was here," Hoosen said as he remembered their conversations while she assisted him with his eThekwini mayoral campaign in last year's municipal elections.
DA leader Mmusi Maimane said Baker was a committed MP, a wonderful and warm person, and a devoted mother and wife.
"I have been in contact with her husband and have conveyed the deep condolences of the entire DA family on their sad loss. Our thoughts and prayers are with them at this time," he said.
"We will continue the hard work that Baker lived so passionately for, but her presence and contribution will be sorely missed. In the coming weeks, the DA will honour her memory in Parliament in the appropriate way. May her soul rest in eternal peace."
The Congress of the People’s Caucus in Parliament also sent it's condolences.
"Tarnia was a humble and committed servant of the people, an activist member of Parliament, and a hard-working and effective member of the Portfolio Committee on Water and Sanitation in the National Assembly. Cope expresses its heartfelt condolences," the party said in a statement.
Political leaders from across the political spectrum tweeted their condolences late on Friday.