The bus driver held out his arm and blocked her from getting off at her stop, the student said.
The child found the gun and put a round in the chamber, police said.
A car crash in February killed Curt Keesee and severely injured his wife, Heather. He left behind four young children.
The trooper's car stopped rolling after it struck an I-beam of a road sign, a news release said.
The district hopes to have results of its tests by Friday.
The sheriff's department said in a news release issued Tuesday that they were first called at 5:22 a.m. Friday about a semitractor in the median on fire about 3 miles east of the Cloverdale exit.
The firearms were allegedly part of 35 firearms stolen from a Cloverdale gun shop.
He told state police he decided to head home but ran out of gas.
Officials estimate the marijuana to hold a street value of $1 million.
Indiana State Police said William Clements and Cassidy Frost were taken into custody about 3:40 p.m. Thursday.