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MANCHESTER (CBSMiami) – A friend of the terrorist behind the Manchester attack says he was upset about the stabbing of a friend last year. The bomber believed no one cared because the victim was a Muslim.

The news comes as specially trained armed officers, for the first time, are patrolling trains in England with the national threat level at critical.

British Prime Minister Theresa May says the investigation into the deadly Manchester concert bombing is making progress.

“Initial searches of premises have revealed items that we believe are very important to the investigation. These searches will take several days to complete,” said Ian Hopkins with the Manchester Police.

Investigators are now working to determine if suspected bomber, Salman Abedi, was part of a much wider terror network. They also want to figure out who constructed the bomb that killed 22 people as they were leaving an Ariana Grande concert.

Authorities have so far arrested eight people in a series of raids in northern and central England Wednesday including Abedi’s brother.

Another brother of Abedi and Abedi’s father, who both live in Libya, have also been detained.

But while there is progress, there’s also outrage over intelligence leaks, possibly from the United States, that officials say could compromise their investigation. British authorities are angry that photos showing the bomb’s detonator, battery, and some shrapnel from the bomb were published by the New York Times.

The New York Times defended its publication of the photos saying they were neither graphic nor disrespectful to the victims.

Prime Minister Theresa May said that she would be sure to discuss this with President Donald Trump while the two attend a NATO summit in Brussels.

“I will make clear to President Trump that intelligence that is shared between our law enforcement agencies must remain secure,” she said.

Families of those who died in the explosion are starting to make funeral arrangements. Dozens more who were injured remain hospitalized, more than 20 of them are listed in critical condition.

Grande was scheduled to perform in London on Thursday and Friday. Her management team announced she’s suspended her tour for the time being. They issued a statement on her behalf which said, in part, “Our way of life has once again been threatened but we will overcome this together.”