Minutes later, the car exploded while being towed, burning a bus and other passing vehicles and leaving two motorists lying on the ground, according to images broadcast by RCN television.
Eight people, most of them bus passengers, were seriously injured in the attack, which may have been perpetrated by leftist rebels in retaliation for a tough new government stance, Colonel Miguel Angel Bojaca, Huila police commander, told reporters.
Gonzalez has received numerous death threats mainly from the Revolutionary Armed Forces of Colombia (Farc), a rebel group which was blamed by local police for Thursday bombing.
"Everything indicates it was an attack against the mayoress by terrorists of the Farc," Miguel Angel Bojaca, a local police commander, said.
The bomb attack came soon after Alvaro Uribe, Colombia's president, visited the region and announced that he would take a tougher line against Farc than his predecessor.
On a visit Tuesday to Huila, whose capital is Neiva, Uribe ruled out any amnesty for leftist rebels under any eventual peace deal, reversing a long-standing blueprint for ending Colombia's five-decade civil conflict.
The 15,000-strong Farc, Latin America's oldest and largest rebel group, had demanded an amnesty during three years of failed negotiations with the administration of Uribe's predecessor.
Neiva has long been engulfed by violence due to its location in the heart of Colombia's impoverished south - a major stronghold of the Farc.