The cause of Flattery's death will be determined by an autopsy, Plymouth Police Chief Michael Botieri said at a press conference outside the school Monday afternoon, but few details about the chemicals in the school were released.

But a little after 8 a.m., when the Plymouth school's main office secretary arrived, she discovered that Chet, the friendly, well-liked head custodian, was unconscious inside. Flattery was dead, and soon 11 others were ill and were taken to the hospital for what police said appeared to be exposure to hazardous chemicals.


He said it did not appear that carbon monoxide had been the cause.

All of those who became ill — mostly emergency personnel who responded to the scene — were treated and released from Beth Israel Deaconess Hospital in Plymouth by early afternoon.

Flattery, 53, had worked at the school for nearly seven years. He arrived at 7 a.m. Monday for typical seasonal cleaning. Classes ended last month, and no students were in the building.

"He came to work like on any other day," said Flattery's wife, Linda.

The couple, who live in Plymouth and have two children, celebrated their 25th wedding anniversary with a cruise in May. Linda Flattery said her husband was healthy — police asked her whether he had any medical conditions — and loved music and books.

She said she was told around 8:30 a.m. that her husband had died, but police had not told her what killed him.

"It was very sudden," Linda Flattery said.

"Chet was an unbelievable person," said Gary Maestas, superintendent of Plymouth's school system. "Every interaction I had over the years was outstanding."

Of the 11 people who became sick, one was a school employee, and the remainder — three police officers, three firefighters, two state troopers, and two paramedics — were first responders who rushed to the school after the secretary reported finding Flattery. Many of the victims reported headaches, Botieri said.


A hospital spokesman declined to give details of their symptoms, but said that being released quickly is "a good outcome." Botieri said they were all released in good health.

Manomet Elementary, a wide brick building set well back from the road behind athletic fields and a playground, was closed Monday as emergency crews from several area public safety agencies came and went. Passersby asked about the scene, with a dozen or more emergency vehicles at the school and television trucks parked along the quiet street out front.

Megan Hokanson, a kindergarten teacher at the school, described Manomet as a small, close-knit school community, "so this is devastating."

She said Flattery was "wonderful, a very much 'give you the shirt off his back' kind of guy."

Dale Powers, who met Flattery about seven years ago through their shared participation in Plymouth County's Defenders Drum and Bugle Corps, said his friend played the contrabass, a brass instrument similar to a tuba, and was always eager to lend a hand.

"He was just such a great guy," Powers said. 'There wasn't a single person in the group of a hundred of us who didn't get along with Chet."

The group marched in a parade in Quincy for the Fourth of July, and Powers said friends of Flattery's spent the day hoping that their worst fears about Monday's news would not be realized.


"He was always the one that was there early," Powers said. "He carried the biggest instrument, but was always willing to help."

Powers was one of many who paid their respects Monday on Facebook, where a few weeks earlier Flattery had bade school staff farewell for the summer.

"I would like to take this moment and thank all the teachers and the staff at MES for another wonderful year," he wrote. "All of you make it a very special place! I will miss every one. Gonna be just my self during the day . . . in the big empty."

Emergency responders had a heavy presence around Manomet Elementary School. George Rizer for The Boston Globe/Globe Freelance

Nestor Ramos can be reached at nestor.ramos@globe.com.