Two officers were shot outside the Ferguson, Missouri police headquarters early Thursday as demonstrators gathered following the resignation of the city's embattled police chief, authorities said.
St. Louis County Police Chief Col. Jon Belmar told reporters at least three shots were fired.
He said a 32-year-old officer from Webster Groves, Missouri was hit in the face and a 41-year-old officer from St. Louis County suffered a shoulder wound.
He said both officers were conscious, but described their injuries as "very serious."
Belmar said he believes the officers were targeted, by someone in the crowd.
Police sources were calling the gunfire an "ambush" and said whoever fired the shots was at large, CBS St. Louis affiliate KMOV-TV reported.
The station says the two victims were standing next to each other, working crowd control.
The shots rang out as a crowd of about 150 people had begun to dwindle, the St. Louis Post-Dispatch reported. Some protesters fell to the ground and others ran. A huge police presence, including officers in riot gear, later surrounded the department.
On Wednesday, Ferguson Mayor James Knowles III announced the city had reached a mutual separation agreement with Police Chief Thomas Jackson that will pay Jackson one year of his nearly $96,000 annual salary and health coverage. Jackson's resignation becomes effective March 19, at which point Eickhoff will become acting chief while the city searches for a replacement.
Jackson was the sixth employee to resign or be fired after a Justice Department report cleared white former Ferguson police officer Darren Wilson of civil rights charges in the shooting of black 18-year-old Michael Brown in Ferguson last summer. A separate Justice Department report found a profit-driven court system and widespread racial bias in the city police department.
The Associated Press contributed to this report.