People in Fort Pierce said the last time anyone paid this much attention to the mosque was in the 1990s, when it first opened, taking over a building that had been a Christian church and removing the cross on the roof.
Inside the mosque - which looks likes a church except for the missing cross - Adel Nefzi, 53, a professor of organic chemistry at Indian River State College, said he and many of those who worshipped with Mateen are trying to collect money and give blood to the victims of the Orlando massacre.
Nefzi, a member of the mosque's board, said he never saw Mateen "interact" with Albusalha, the suicide bomber who went to Syria. He said he does not believe there is any link between the two.
"It's our bad luck," he said, that both violent men had connections to this little mosque, one of the oldest in this part of Florida. The Fort Pierce mosque has drawn people from other parts of central Florida, including Abusalha, who had lived farther north, in Vero Beach, before leaving for Syria.
"We are frustrated and horrified" by the mass shooting at a gay nightclub in Orlando that had down worldwide attention and more local scrutiny, Nefzi said. He said Mateen "has not done this because he is a Muslim but because he has a psychological problem".
"We don't teach anything" against homosexuality in the mosque meetings, he said. Asked what he personally believed about the lifestyle of gay people, he said, "It's the wrong thing, but for sure we have no right to judge people. . . . We are in shock, horrified".
Nefzi sat under whirring fans in the green and white room where he saw Mateen for the last time. He said between 100 and 150 others were there for evening prayers, and Mateen had his young son with him. Mateen didn't mingle but left as soon as prayers were finished, Nefzi said, adding, "He was not very religious."
Another Muslim who worshiped at the Islamic Centre here and who didn't want to be named said he heard Mateen talk of "immorality" in the United States and specifically mentioned a recent Texas case of a female teacher having sex with an eighth-grade student - without objections by the boy's parents. "I don't think this is an Isis-condoned attack, I think it's a hate crime," said the man.
Either way, people in Fort Pierce are shocked.
"This has taken us aback," said Linda Hudson, the Mayor of Fort Pierce. "This could be Anywhere USA."
"This is little Fort Pierce!" said Donna Lages, 39, a waitress at the Golden Bear restaurant, which serves a US$4 breakfast special. She said the place prides itself on its blend of races and religions, and people in Fort Pierce see it as a strength that everyone is from somewhere else.
At a chemist near the mosque, a middle-aged cashier was shaken by the harsh talk about Muslims she has heard since the shooting. "One guy came in and said maybe we should start killing them if they are killing us," said the woman, who like many in the town did not want to be quoted by name because of the sensitivity of the issue. "Too much hate," she said, blaming some of it on presidential candidate Donald Trump. "I know people are saying Trump will be tougher on Muslims, but I think he is causing a lot of this," she said.
This has taken us aback. This could be Anywhere USA
Debbie Kepler, the organist at the Midway Baptist Church, which is on the same street as the mosque, remembered when it still had a cross and Christians.
Now, she said, the Christians and Muslims don't mix much.
"We don't go over there and they don't come over here," she said. She blamed the violence on a "disturbed person," not on his religion, and said it was unnerving to wonder why he drove two hours north to Orlando when there are people closer to home he might have wanted to kill.
