Two women who knew the man who was fatally shot by state troopers after stopping his pickup on Seattle’s Ship Canal Bridge on Monday say he was battling mental illness.

Jonathan Whitehead, 33, was reportedly driving his brown pickup erratically, weaving in and out of lanes and speeding, before coming to a stop on the southbound lanes of Interstate 5.

Whitehead allegedly set the vehicle on fire and then grabbed a can of green spray paint to vandalize other cars and the pavement, according to witnesses and the State Patrol.

When two troopers arrived, Whitehead confronted one of them with a knife, the State Patrol said. One trooper fired a Taser at the man, but it didn’t work and when the armed man continued approaching them the two troopers opened fire, the State Patrol said.

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Whitehead died from multiple gunshot wounds, the King County Medical Examiner’s Office said Wednesday.

One relative by marriage, who did not want to be named, said Whitehead “had a very, very good heart. It’s a tragedy.” That woman’s mother said Whitehead was mentally ill but did not provide details. Neither woman wanted to speak at length, saying the family is grieving.

Little is known about Whitehead. His last address was in Marysville and he was cited for several traffic infractions, including operating a vehicle without insurance, in August and December 2012. He doesn’t appear to have had a criminal record in Washington state. He has ties to Kansas.

Seattle police, who are leading the investigation, have not released any details about Whitehead or why they think he behaved so erratically. “We have nothing new and will likely not have anything new for some time,” Seattle police spokesman Sgt. Sean Whitcomb wrote in an email.

The troopers who opened fire, Andrew Boyer and Christopher Kyle, remain on administrative leave while the case is investigated.

The shooting and subsequent investigation resulted in the southbound lanes of I-5 being shut down for nearly five hours.

Jennifer Sullivan: 206-464-8294 or jensullivan@seattletimes.com On Twitter @SeattleSullivan