Prosecutors have decided that the employees and owner of a welding company responsible for a fire in a Boston brownstone last year that killed two firefighters will not face criminal charges.

Suffolk County District Attorney Daniel Conley said Tuesday that the actions of the D&J Ironworks employees and ownership, while "irresponsible and even careless," were not "willful, wanton, and reckless" enough to support criminal charges.

The fire in the city's Back Bay neighborhood in March 2014 took the lives of Lt. Edward Walsh and firefighter Michael Kennedy. They died from smoke inhalation and burns when they were trapped in the building's basement.

Investigators determined that the wind-whipped fire was started by welding sparks from work being done without a permit at the building next door.