Reading, England CNN  — 

A 25-year-old man suspected of launching a fatal terror attack in Reading, England on Saturday has been identified by a security source as a Libyan national.

Speaking to CNN, the security source named the suspect as Khairi Saadallah. The source said mental health was considered to be a factor in the assault, which contributed to the reasons police took some time to declare it a terrorist incident.

Saadallah, who is currently in police custody, is under investigation by the UK’s Counter Terrorism Policing unit after a knife attack in Reading’s Forbury Gardens on Saturday afternoon that left three dead and several others injured.

UK Assistant Commissioner for Counter Terrorism Policing, Neil Basu, said no further suspects are under investigation by the police.

Police block the entrance near Forbury Gardens in Reading town center.

“I am deeply saddened by the events of last night. This was a truly tragic incident and the thoughts of Thames Valley Police are with all those who have been affected,” Chief Constable John Campbell of Thames Valley Police said Sunday.

“Incidents of this nature are very rare, though I know that will be of little comfort to those involved and understand the concern that this incident will have caused amongst our local community,” he added.

Emergency services at Forbury Gardens in Reading town center responded to the incident, where three people died.

Eyewitness Lawrence Wort, who was in the park at the time of the attack, told CNN that people were relaxing and enjoying the sun when he heard a man shouting and yelling. The man began to approach people in the park, and started to stab people in the neck and under the arms, and attacked multiple people in this way, Wort said.

A CNN team saw counter-terrorism police at an apartment block, who were combing for evidence early into the morning. Police asked some residents to stand outside their work so they could carry out their work.

Armed police officers work at a block of flats in Reading after an incident at Forbury Gardens park in the town centre of Reading, England, Saturday.

UK Prime Minister Boris Johnson said on Sunday that he was “appalled and disgusted” by the incident, but that he saw “no reason” to raise the country’s terror alert level.

“I am appalled and disgusted that people should lose their lives in this way and our thoughts are very much with the families and friends of the victims today,” he said.

Johnson said he had spoken to the Chief Constable of Thames Valley police, and “thanked him and his officers for their bravery in tackling the suspect.”

The police have urged members of the public to avoid the area, confirming that cordons remain in place; they have also called for witnesses to come forward with information.

“We would like to hear from anyone who has video footage. Out of respect for those deceased and injured, along with their loved ones, please do not circulate this footage on social media – this will be incredibly distressing,” Chief Constable Campbell said.

“From our enquiries undertaken so far, officers have found nothing to suggest that there were any other people involved in the attack, and presently, we are not looking for anyone else in relation to this incident,” he said in a statement, adding that detectives were working with security services to ensure there was “no related outstanding threat to the public.”

Basu also noted that the incident was not at all associated with a peaceful Black Lives Matter protest, which took place earlier in the day and concluded hours before the attack.

Salma Abdelaziz reported from Reading, Nada Bashir and Amy Woodyatt wrote in London. Sharon Braithwaite, Arnaud Siad, Dakin Andone and Mitchell McCluskey contributed to this report.