A spokesman for the Clay County Sheriff’s Office told The Kansas City Star that a deputy spotted smoke from the burning van during a traffic stop and arrived at the scene around 2:30 p.m. The deputy approached, but retreated at the sound of the ammunition going off.

The van’s owner, who the report did not identify, allegedly told the deputy that he attempted to quash the flames by driving the vehicle back and forth over them until the tires also caught fire. He said he evacuated the area at that point because he realized that the van was full of firearms ammunition and had a full tank of gas, according to the report.

It was unclear what type of ammunition was in the van, according to the report. But the unidentified owner told local TV station WDAF that a loaded gun he’d stored under the van’s passenger seat discharged a few times.

The Kansas City Star reported that the Liberty Fire Department responded to the blaze and the van’s owner wasn’t immediately cited.