UPDATED 07/08/16 12:43 a.m.
DALLAS (CBSNewYork/CBS DFW) -- Eleven police officers were shot, and four of them were killed Thursday night in Dallas during protests against police brutality.
Dallas police Chief David Brown reported that two snipers shot 11 police officers from elevated positions during the protest. Three officers were killed in the shooting, two more were in surgery, and three more were in critical condition, Dallas police said.
Two of the officers killed were Dallas Police officers, a third was a Dallas Area Rapid Transit officer, it was not immediately clear which department the fourth officer worked for.
Police reported early Friday morning New York time that two suspects were in custody in connection with the shooting.
Police said one man turned himself in after his photo was circulated, and said another suspect was also in custody after a shootout with Dallas SWAT team officers.
Police said a suspicious package was found near the second suspect's location, and the Dallas Police Bomb Squad was defusing the package.
Police had earlier reported that that the suspects had threatened to plant a bomb in the downtown Dallas area. Brown said his department had reached out to the FBI and the Bureau of Alcohol, Tobacco Firearms and Explosives to search for the suspects and "do a very thorough search of this area where we believe there might be a bomb planted."
Dallas police had earlier tweeted out a photo of one man whom Brown said was a "person of interest." Brown noted that the man was wearing camouflage and had a rifle strapped over his shoulder.
However, march co-organizer Cory Hughes was quick to claim police had the wrong man. He said the man whose photo police tweeted out was his brother Mark Hughes, who was carrying the gun as allowed by his Second Amendment rights.
Hughes said he asked his brother to hand the gun over to a police officer, and told KTVT-TV, CBS11 in Dallas that Mark gave the gun to an officer and went home.
"That's my little brother. That's not the suspect," Cory Hughes said. "He just walked away."
But police said the man in the photo later surrendered to officers.
Dallas police also apprehended two people on I-35E, after an officer saw one person carrying a camouflage bag walking quickly down Lamar Street. The person threw the bag in the back of a black Mercedes and sped off in the car, police said.
Officers pursued the car down the expressway and were questioning both people who had been in the car early Friday.
Dallas Mayor Mike Rawlings asked the city to join him in supporting the police department.
"Let's all come together and support our police officers," he said. "I've never been as proud. I believe we've got to one of the best forces in the nation, and we've done things with civil rights in the right way, and we've done it for the safety of our citizens. So please, let's come together now as a city."
One of the transit officers who was shot and survived was identified by her father as Misty McBride. He said his daughter has been a transit officer four about five years, and was wounded in the shoulder and abdomen.
No other officers' identities had been released early Friday.
KTVT reported that shots rang out around 9:45 p.m. New York time in downtown Dallas. Police ordered the clearing of all streets in downtown Dallas late Thursday night.
KTVT reported that a peaceful group of protesters gathered at Belo Park in Dallas Thursday evening, to demonstrate against the police shootings that killed African-American men in Minnesota and Louisiana this week.
But on Thursday night, shots were heard at a the top of a building as the protest was in progress below, KTVT reported.
KTVT reporter Ken Molestina reported that he heard upwards of a dozen gunshots. Others quoted an even larger number of shots.
Organizer Hughes said his group had just finished with a speech on the courthouse steps, and saw people running. He said he heard about 20 gunshots in succession.
"It's just bananas," Hughes said.
Hughes said he not heard about any threats ahead of the protest.
Clarissa Myles told KTVT she was eating at a nearby McDonald's when the chaos began.
"Everyone was screaming, people were running. … I saw at least probably 30 shots go off."
Myles also said she saw two men who were "super upset" with police right before shots rang out. She was shocked that the peaceful protest could take such a sinister turn so quickly, KTVT reported.
"Are they really shooting? This was a peaceful protest," said Myles.
Protesters were out in Dallas and around the country after a police shooting that killed Philando Castile in Minnesota. The aftermath of the shooting was streamed live on Facebook.
Diamond Reynolds started recording moments after police officers shot Castile, her boyfriend, during a traffic stop in Falcon Heights on Wednesday.
Meanwhile, two officers were also placed on administrative leave in Baton Rouge, Louisiana after cell phone video captured the moment 37-year-old Alton Sterling was shot outside of a convenience store.
for more features.