Belgian authorities said Friday that the lone assailant who killed one police officer and wounded another in a stabbing attack had been on a counterterrorism list of potential extremists.

The Belgian suspect, who had served six years in prison for common-law crimes, had gone to a police station early Thursday to express hatred for them, but couldn't be arrested before he launched his stabbing attack on two police officers that evening.

"The man was on the list of OCAD," said federal prosecution magistrate Eric Van Der Sypt, referring to the organization that assesses the terrorism threats in Belgium.

Van Der Sypt said the suspect shouted "Allahu akbar," the Arabic phrase for "God is great," during the stabbing attack, which occurred around the usually busy Brussels Nord station just after evening rush hour.

The suspect was identified as Yassine M, born in Brussels in 1990. His common-law crimes put him behind bars between 2013 and 2019.

On Friday, he faced charges of "murder and attempted murder within a terrorist context," Van Der Sypt said.

Brussels prosecutor spokesperson Sarah Durant said the suspect had made "unhinged remarks" during a discussion with officers hours before the attack. Since he voluntarily asked for psychological help, he wasn't arrested and was instead sent to a hospital, which he left soon after.

After the stabbings, the suspect was almost immediately shot and wounded by another police officer who had rushed to the scene. The condition of the attacker wasn't disclosed, but authorities said that he was still hospitalized Friday and unable to be interrogated.

Belgian authorities kept the overall terrorist threat level at two out of a possible four, meaning the risk of an attack was "medium."

Belgian Prime Minister Alexander De Croo posted a message of condolences to the family and friends of the dead officer.

"Our police officers risk their lives every day to ensure the safety of our citizens," he said. "Today’s tragedy demonstrates this once again."

Interior Minister Annelies Verlinden said she was in contact with the Brussels mayor, police chief and security services to coordinate the response to the attack.

"Such violence against our people is unacceptable," she said.

Authorities came under immediate criticism for not arresting the suspect when he made his initial threats to the police early Thursday, but Durant said procedures stipulate that he had to be taken by police to a hospital since he had asked for psychological help himself.

"Police remained there until hospital staff took over," she said. A few hours later, when police checked on his whereabouts, "it appears that the person had left the hospital."

The attack touched a nerve in a nation that has been hit by several attacks in the past decade, including suicide bombings in 2016 that killed 32 people and injured hundreds more in the Brussels subway and airport.