(CNN)The calls are fast and frantic as gunshots echo in the background. "Priority -- shots fired! Shots fired!" a voice says, getting louder with each declaration.
Other voices follow, at times speaking over one another. One repeats the address where gunfire broke out -- over and over.
Police scanner captured the chaotic first few minutes when gunfire erupted while officers were serving a narcotics warrant at a row house in North Philadelphia. On scanner traffic, the grim declarations come in a flurry from different unidentified people.
"Officer down!" one voice says.
"We need SWAT!" another person yells.
"Get me SWAT, ASAP! Long guns, ASAP!" one loudly interrupts.
Others implore faster action, the urgency evident in their words.
"This is the second call ... shots fired at police!" one says.
"I've got an officer shot, radio!" one voice says at times cracking. "Radio, listen. I've got one officer shot, one officer shot, radio!"
Six Philadelphia officers were shot by at least one gunman who opened fire Wednesday afternoon, according to the police department. The standoff entered its sixth hour late Wednesday night with at least one barricaded suspect in the home.
Negotiators are trying to communicate with the shooter, but he's picking up the phone and not saying a word, Philadelphia Police Commissioner Richard Ross Jr. said.
CNN's Chris Boyette contributed to this report