(Reuters) - Two sheriff's deputies were shot dead and two wounded in LaPlace, Louisiana on Thursday by an attacker armed with an assault weapon , police said.
The gunman shot one St. John Parish deputy while he was directing traffic in an off-site parking lot for the Valero Energy Corp 's St. Charles refinery , Sheriff Mike Tregre said.
The gunman fled the scene, and officers investigating the incident ended up at a trailer at a trailer court. While they interviewed two suspects, a person came out of the trailer with an assault weapon and fatally "ambushed" two officers, he said.
"At this point, it's a very hot investigation and it's ongoing," Tregre said at a televised news briefing.
Five people are believed to be in custody. Some suspects were shot and wounded, he said.
Details were still sketchy, but Tregre said: "There are no other perpetrators on the loose."
The slain deputies were identified as Brandon Nielsen, 34, and Jeremy Triche , 28. The wounded deputies were identified as Scott Boyington and Jason Triche.
The Louisiana State Police have taken over the investigation and are looking into what led to the initial shooting. A State Police spokeswoman told CNN that two of the officers were off-duty and two were on duty.
LaPlace is about 25 miles west of New Orleans. Valero said in a statement that refinery operations were not affected.
(Reporting by Ian Simpson and Colleen Jenkins; Editing by Vicki Allen and David Brunnstrom)