There was chaos and screaming at the Ariana Grande concert at the Manchester Arena on Monday evening after a lone suspect, carrying a bomb, caused an explosion that killed at least 22 people, including children. 59 others were injured in what is being considered by Manchester Police to be a terrorist attack. The concert hall can host 21,000 people.

Explosion at Ariana Grande concert caused by suicide bomber

Chief Constable Hopkins said in a news statement that the attacker had detonated an “improvised explosive device,” killing himself and 22 others and injuring at least 59 people.

Police currently believe the suspect was acting alone, but investigations will be carried out to find out if the suspect was part of a network. The explosion reportedly occurred in a public area at the arena, outside of any security screening.

Hopkins said Tuesday morning that there were at least 400 police deployed in the area surrounding the Manchester Arena overnight. Hopkins went on to say that residents in the area should expect to experience more armed police officers on the streets of Manchester. Should the latest attack be confirmed as a terrorist incident, it would be the worst and deadliest terror attack in the U.K. since the 7/7 London bombings in 2005, where 52 people were killed.

U.K. Prime Minister Theresa May has called the bombing an “appalling terrorist attack” and the U.K. government will hold an emergency committee meeting on Tuesday.

Bomb explodes as Ariana Grande concertgoers start to leave the Manchester Arena

The New York Times reports that the explosion rocked the arena just as concertgoers – many of which were young fans of Grande – were starting to leave the concert after the singer’s closing set.

People fled in panic, while sirens were heard around the area.

As reported by CNN, one witness, Calvin Welsford, 18, said he heard the “loud bang” minutes after Grande’s set concluded at around 10:30 p.m.

Many posts on social media showed the panicking concertgoers fleeing down the stairs at the arena to get away. Manchester Royal Infirmary, the local hospital, was told to prepare for what was considered a major incident.

Grande – who is currently on a European and Latin America tour – was not injured in the explosion and took to Twitter to say the terror incident had left her feeling “broken.” She said she was so sorry and had no words.

Suicide bombing at Manchester Arena

U.S. Department of Homeland Security official has said suicide bombing is considered to be the probable cause of the blast and that a male at the Manchester Arena has been identified as the likely Suicide Bomber.

The department said in a statement that it is “closely monitoring” the circumstances surrounding the explosion, but added that there is nothing to indicate a credible threat to music venues in the U.S.

According to U.K. Home Secretary Amber Rudd, the terror attack was aimed at the most vulnerable in U.K. society as there were young people and children at the Ariana Grande concert. She warned Britons to remain “alert, not alarmed” after the terror attack.

Manchester opens its heart to Ariana Grande concertgoers

Residents in Manchester are reportedly opening their doors to offer a safe space to assist concertgoers after the incident. Taxi drivers in the city are offering free rides to concertgoers needing transport as the train station has reportedly been locked down.