(CNN) -- A man suspected of fatally shooting two Tampa, Florida, police officers is a suspect in another homicide and is sought for questioning in two others, Police Chief Jane Castor said Thursday.
All the homicides have taken place since Dontae Morris was released from prison in April, Castor told reporters.
"We just want to make the public aware of who we're dealing with here in Dontae Morris," she said. "... he's a cold-blooded killer."
Morris, 24, is accused of shooting Officers Jeffrey Kocab and David Curtis during an early-morning traffic stop Tuesday near downtown Tampa. The officers, both 31, later died at a hospital.
Morris is also suspected in the killing of a man at an apartment complex, Castor said. That homicide occurred May 18, according to the Tampa Tribune.
"We are continuing to track down some very, very positive leads," the chief said, and police remain confident Morris will be apprehended.
She said she didn't believe the community was at risk, but said Morris could be moving about, and the situation could be "unpredictable."
Meanwhile, Morris' picture was featured on FBI billboards in Florida, Georgia and Alabama, authorities said Thursday.
Although it's not the first time authorities have featured fugitives' pictures on billboards, the posting of Morris' photograph marked the first time authorities could post such images themselves, through a partnership with outdoor advertising companies, said Chris Allen, spokesman for the FBI's Tampa bureau.
"Beforehand, it would have taken the better part of a day or two" to get the photos up by contacting the companies, he said. While the initiative was on standby for the Times Square bombing attempt, it was not used, he said.
The billboards went up in Florida shortly after the crime occurred Tuesday, he said. Authorities recently decided to feature the picture in Alabama and Georgia. Other states can be added, too, he said -- authorities simply create the alert on a computer and use a drop-down menu to select states.
Asked whether officials plan to use the billboards in other states, Allen said it depends on where the investigation leads authorities.
Morris' picture and information was also put on the website of the television program "America's Most Wanted."
Meanwhile, Tampa police said Wednesday afternoon the reward for information leading to Morris' arrest has increased to $100,000 -- the biggest in the city's history.
"The intensity will keep up until we capture him," said Tampa Mayor Pam Iorio. Anyone helping or harboring Morris is "making a huge mistake," she said.
Asked about some citizen complaints about being inconvenienced by the ongoing search, Castor said, "I am very sorry for anyone's inconvenience. We don't want to inconvenience anyone, but our ultimate goal is to keep the citizens of Tampa safe ... I believe that anger should be focused on Dontae Morris. He's the one that's causing all this."
Iorio said the evacuation of a building or the closure of a street is a "small inconvenience" given what authorities are trying to do.
Asked about officers' anger toward Morris, Castor said police are "reeling over the loss of two family members" but are professionals who will take Morris into custody safely if at all possible. She reiterated, however, that the best course of action would be for Morris to give himself up.
Authorities have arrested several of Morris' associates, she said. According to CNN affiliate Bay News 9, police are also searching for Morris' 21-year-old brother for questioning.
Public services for the fallen officers will be held Friday evening at a church in Lutz, Florida, Bay News 9 reported. Funeral services are planned for Saturday.
The officers were shot after Curtis pulled a vehicle over about 2:15 a.m. ET Tuesday, and the driver -- identified by police as Cortnee Brantly -- gave him identification and vehicle registration that did not match the vehicle, Castor said. Running a criminal history check, Curtis found that the passenger -- identified as Morris -- had an outstanding misdemeanor worthless-check warrant from Jacksonville, Florida.
Curtis called for backup, and Kocab responded, police have said. As the two attempted to arrest the suspect, he pulled out a gun and shot them both, Castor has said. A gun was not found at the scene, she said, and police believe Morris still has it.
Brantly was taken into custody Tuesday and authorities released her after seven hours of questioning, Castor said. Brantly provided police with information, she said, but "I would not describe her as cooperative." Although police had enough information to arrest Brantly, their focus is on apprehending Morris, the chief said.
She defended the decision to release Brantly, saying "there is still a very, very distinct possibility she will be charged down the road ... The community needs to trust in the ability of the TPD."
Kocab's wife is due to give birth next week, police said at the time of the shootings. Curtis leaves a wife and four sons, ages 9, 6, 5 and 8 months.