READING, England (CBS/AP) -- Eyewitness News has learned one of the victims of a stabbing rampage that killed three people as they sat in a British park on a summer evening is from Philadelphia. Joe Ritchie-Bennett was one of three people killed Saturday in what British investigators are labeling an act of terror.
Ritchie-Bennett was a graduate of Father Judge High School. He lived in the United Kingdom for the past 15 years. His family still lives in Philadelphia.
His father, Robert Ritchie, told Eyewitness News, "The family is heartbroken they have lost their brilliant and loving son. This was senseless."
A 25-year-old man who is believed to be the lone attacker was in custody, but officials said the motive for the carnage was unclear. Authorities said they were not looking for any other suspects and they did not raise Britain's official terrorism threat level from "substantial."
Ritchie-Bennett and two other people were killed and three others seriously wounded in the stabbing attack that came out of the blue Saturday in Forbury Gardens park in Reading, a town of 200,000 people 40 miles (64 kilometers) west of London.
"Motivation for this horrific act is far from certain," said Neil Basu, Britain's top counterterrorism police officer, as police forensics officers combed the park for evidence.
Chief Constable John Campbell of Thames Valley Police said officers were called to reports of stabbings just before 7 p.m. and arrived to find a "horrific" scene. He said a suspect was apprehended within five minutes.
Basu said "incredibly brave" unarmed officers detained a 25-year-old local man at the scene. Police said they did not believe there was any further danger to the public.
Police have not identified the suspect, but Britain's national news agency, Press Association, and other media outlets named him as Khairi Saadallah, a Libyan asylum-seeker living in Reading.
A Reading man of that name who is the same age as the suspect was sentenced to two months in prison last year for assaulting an emergency worker. The same man was also charged last year with assaulting a judge who had sentenced him.
The BBC reported that Saadallah was investigated by British security services last year over concerns he planned to travel abroad to join a jihadi group, but that he was not determined to be a major threat.
Prime Minister Boris Johnson, who met security officials, police and senior ministers on Sunday for an update on the investigation, said he was "appalled and sickened" by the attack.
"If there are lessons that we need to learn" or legal changes needed to prevent such attacks, "then we will learn those lessons and we will not hesitate to take action where necessary," Johnson said.
Police officers patrolled cordons on the roads leading to the park on Sunday, and blue-and-white tents were erected near the attack site. Overnight, heavily armed officers entered an apartment about a mile away, and a loud bang was heard.
Notes and bunches of flowers had been left Sunday by the police tape in tribute to the victims. One of the people killed was identified as James Furlong, a teacher in the nearby English town of Wokingham.
"There are no words that anyone can say to express how horrible and senseless this was," one said. "Our prayers are with all the victims and their families and friends. #Readingstandsunited."
The attack came hours after a Black Lives Matter demonstration at Forbury Gardens, but police said there was no connection between the two events.
Personal trainer Lawrence Wort said the park was full of groups sitting on the grass Saturday evening when "one lone person walked through, suddenly shouted some unintelligible words and went around a large group of around 10, trying to stab them."
"He stabbed three of them severely in the neck and under the arms, and then turned and started running towards me, and we turned and started running," Wort said.
Britain has been hit by several terror attacks in recent years, both by people inspired by the Islamic State group and by far-right extremists. Islamist-inspired attacks include a suicide bombing at an Ariana Grande concert in Manchester that killed 22 people in 2017 and two deadly vehicle and knife attacks in London the same year.
In several cases, attackers have been known to police. In November, a man who had been released after serving a prison sentence for a terrorism offense stabbed two people to death at a justice conference in London.
In February, a man recently released from prison after serving time for terrorism-related offenses strapped on a fake bomb and stabbed two people on a busy London street before being shot to death by police. No one else was killed.
Britain's official terrorism threat level stands at "substantial," the middle level on a five-rung scale, meaning an attack is likely.
(© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)
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