SPRINGFIELD, Ill. (WAND) - Authorities said the suspect in a deadly Springfield shooting used two handguns in the attack, and finding a motive may never happen.

"We will work diligently and exhaust all leads and efforts to provide answers to the victims families but in the end, we may not be able to," Springfield Police Chief Kenny Winslow said.  

In a Wednesday press conference, Winslow said their investigation into the June 26 shooting at the Bunn-O-Matic warehouse revealed Michael L . Collins, 48, walked up to victims Christopher Aumiller and Bill Gibbons and shot them in close proximity at their work stations. The third person killed, Marsha Strumpher, was shot outside as Collins was leaving the area. 

Collins then left the scene of the shooting. Morgan County authorities later found him dead in his vehicle. Police said he had shot himself.

"We believe he is the lone suspect," Winslow said. "We don't believe he worked in conjunction with anyone else. We believe he is the lone suspect."

Police said Wednesday a Morgan County deputy was dispatched to a slumped driver at about 1:20 p.m. on June 26. They arrived and found the vehicle matched the description of the suspect vehicle in the Springfield shooting. 

There were two 9 mm handguns inside of the vehicle. Police said they determined Collins had a valid FOID card and purchased those guns at a local sporting goods store. One gun was used on Aumiller and Gibbons, while the other was used on Strumpher. 

Winslow said Wednesday Collins was able to leave the area before the first officer arrived on the scene. The chief said past training at the facility helped them in their response because officers knew the layout of the warehouse.

"It is something that we do in our larger faculties to make sure that we have that information," he said. "There are certain things we do, that I won't get into here, but then if an incident does occur, we can draw from it." 

A motive in the shooting remains unclear, police said. Authorities did say Aumiller, Gibbons and Collins worked in the same department at Bunn-O-Matic.