CHICAGO (CBS) – The two Chicago Police officers who were fatally struck by a train Monday night were pursuing a shooting suspect after gunfire was detected by a system called ShotSpotter.

ShotSpotter ShotSpotter Helps Officers Respond Faster, But Puts Them In More Danger, Police Say

ShotSpotter increases the chance of officers catching shooting suspects, but it also can make an officer’s job more dangerous.

It did that Monday night for the two officers pursuing a shooting suspect on the railroad tracks when they were hit by the outbound South Shore train. They got to the scene so quickly they were able to chase the suspect.

“Certainly because we are getting there quicker we are catching the individuals, and that does pose a greater danger to our officers,” said Fraternal Order of Police President Kevin Graham.

They are getting there faster because of ShotSpotter technology. The sensors record the sounds of gunfire and quickly show police exactly where to go to search for the shooter.

“The officers can actually arrive to the scene somewhere between five and seven minutes before a 911 call, and that gives us more opportunity to arrest the offender and actually intervene in some crimes,” Chicago Police Supt. Eddie Johnson said.

In one incident last May the sounds of gunfire were caught by ShotSpotter, which sent officers to a porch to investigate. One suspect took off, leading to a foot chase down an alley. The offender turned, and police shot him.

A gun was recovered from the incident – a potentially life-threatening situation for officers.

For now the FOP and city officials agree the ShotSpotter program is helping the city battles its crime problem.

“That’s not a bad thing for the city of Chicago,” Graham said.

But it ended tragically for Officers Eduardo Marmolejo and Conrad Gary.

“They were responding to ShotSpotter, doing their job, trying to protect the rest of us,” said Mayor Rahm Emanuel.

In September ShotSpotter announced a multiyear, $23 million deal with the Chicago Police Department. It covers 12 police districts, about half of the city’s districts.