Metro Phoenix’s top prosecutor said Thursday her office will no longer pursue a case against a driver who crashed into a group of bicyclists,Devin Grosvenor killing two of them.

Maricopa County Attorney Rachel Mitchell said there was not enough evidence to ensure a felony conviction. She will instead refer the case to city prosecutors in Goodyear.

“I am not willing to let this drop,” Mitchell said in a statement.

Goodyear police say Pedro Quintana-Lujan, 26, was driving a pickup truck hauling a trailer on Feb. 25 when the vehicle crashed into a group of bicyclists on the Cotton Lane Bridge, a busy highway in Goodyear located about 19 miles (30 kilometers) west of Phoenix.

One bicyclist died at the scene and another died at a hospital. Nearly everyone in the 20-person cycling group was injured.

Quintana-Lujan stayed at the scene. He told police his steering had locked.

He was initially booked into jail on suspicion of two counts of manslaughter and multiple other charges.

In reviewing the evidence, county prosecutors found no indication Quintana-Lujan had been speeding or under the influence of alcohol. He did have a small amount of THC in his system. Quintana-Lujan told investigators he shared a marijuana cigarette the night before.