The Department of Homeland Security has issued a press release, stating in part:

At this time, we have no information to indicate a specific credible threat involving music venues in the United States. However, the public may experience increased security in and around public places and events as officials take additional precautions.

The head of the Manchester Police would not say at the latest press conference if anyone has been arrested. But NBC News is reporting the body of a suicide bomber was found at the scene and has been tentatively identified:

From NBC:

Multiple senior U.S. law enforcement officials briefed by British authorities told NBC News that forensic evidence at the scene — including a body found at the blast site — indicated a suicide attack. British and U.S. law enforcement officials said they believed they had tentatively identified the bomber.

In the 9th issue of ISIS' recent Rumiyah 9, an English Magazine (no link, but I saved a copy when it came out) there was an article on terror tactics and hostage taking. It included this:

Ideal target locations for hostage-taking scenarios include night clubs, movie theaters, busy shopping malls and large stores, popular restaurants, concert halls, university campuses, public swimming pools, indoor ice skating rinks, and generally any busy enclosed area, as such an environment allows for one to take control of the situation by rounding up the kuffar present inside and allows one to massacre them while using the building as a natural defense against any responding force attempting to enter and bring the operation to a quick halt.

Similarly, characteristics of a good target location include low light conditions, as it grants one the ability to maneuver between the people, taking advantage of the confusion and killing as many of the kuffar as physically possible.

Al Qaida has plotted attacks at public places in Manchester before. From a DOJ press release in 2015 on the conviction and 40 year sentence of Abd Nassr.

The defendant and his accomplices came within days of executing a plot to conduct a bombing at a crowded shopping mall in Manchester, England, as directed by senior al-Qaeda leaders in Pakistan.

That particular planned attack, which also targeted the New York City subway system and a newspaper office in Copenhagen, had been directed by and coordinated with senior al-Qaeda leaders in Pakistan. Nassr is the eighth defendant to face charges in federal court related to the al-Qaeda plot, which also involved Adis Medunjanin, Najibullah Zazi and Zarein Ahmedzay, the three members of the cell that targeted New York City. Naseer was convicted in March 2015 after a three-week jury trial of providing material support to al-Qaeda, conspiring to provide material support to al-Qaeda and conspiring to use a destructive device in relation to a crime of violence.

I'm sending goodthoughts to the children, teens and their parents who have been hurt, traumatized and emotionally scarred by this event. I suspect by morning here, we'll know the attackers name and if he acted alone.

I've stated my opinion here many times over the past five years covering ISIS that the threats the West has to worry about are not from returning fighters, but homegrown fighters that never got a chance to go fight in Iraq or Syria. These are the ones Al Qaida and ISIS are trying to inspire -- telling them not to travel, and just act on their own in their home country. The result will be the same and they will still be rewarded as if they had died on a battlefield.