Houston Mayor John Whitmire vowed Friday to "pursue an independent and transparent" local investigation into Tuesday's deadly ICE shooting but said federal control over evidence is proving difficult to overcome.

Whitmire said he directed Houston Police Chief Noe Diaz to be "proactive" in pursuing an investigation amid witness statements that contradict ICE's account of the fatal shooting of 52-year-old Lorenzo Salgado Araujo.

Diaz has a meeting with Houston's FBI bureau chief next week, Whitmire said, adding that the chief asked the federal agency to "start sharing information." "Our hands have been tied, but I've instructed the chief [and] city attorney to untie those hands," Whitmire said in an afternoon news conference.