Three Maine women – Sabina Grasso, Anna McDonough and Caitlynn Brown – went to TD Garden to watch a Boston Bruins hockey game Thursday night and belatedly celebrate Grasso’s 21st birthday several days earlier.

But instead of a celebration, Grasso and McDonough were transported to Massachusetts General Hospital after a metal pole used to hold up protective netting suddenly swung down from the ceiling, striking each of them in the head and knocking Grasso unconscious.

At the time, the game had ended and the three women were standing next to the glass behind the goal area and the netting, taking photographs commemorating their night out. The women have been friends since they met as freshmen at Emmanuel College in Boston, even though they now attend different New England colleges.

The netting was mandated by the National Hockey League in 2002 to protect spectators from stray pucks, after a puck hit and killed a 13-year-old girl in Columbus, Ohio.

McDonough and Grasso were both at their parents’ homes in Scarborough and Cumberland Foreside, respectively, on Sunday night, recovering from concussions and emotional trauma.

McDonough’s father, Brian McDonough, a lieutenant with the Maine State Police, said the accident is being downplayed by TD Garden officials. The two women’s injuries are anything but minor, he said.

“These were not minor injuries. These women are lucky to be alive,” McDonough said in a telephone interview Sunday. “The photographs (online) speak for themselves.”

McDonough, who heads up major criminal investigations for the state of Maine, said he wants answers about what happened.

Several people were still in the arena when the accident took place after the game against the Washington Capitals. One of them – an eyewitness, who was sitting about 15 feet away from the women at the time – told the Portland Press Herald on Sunday night that the metal pole attached to the protective netting came down without any warning.

“It was very strange that it just fell. A security guard told me it was a freak thing that happened,” said Jared Wickerham, a staff photographer for Getty Images who is based in Boston.

Wickerham, who regularly covers Bruins games, said he did not see any of the TD Garden staff trying to raise the netting when the pole suddenly swung down and hit two of the women. It made no sound when it dropped. An object in front of him blocked the pole from hitting Wickerham. His camera, however, was destroyed.

“It happened so fast. There was no warning,” Caitlynn Brown, who lives in Portland, said in a telephone interview Sunday. Brown, a junior at the University of Maine in Orono, said she is still shaken by what happened.

“I’m doing OK, but it was really scary. You never think about something falling from the sky and knocking out your best friend,” she said.

Brown, 20, said she rushed to Grasso’s aid, using her own jacket to stem the flood of blood from her head. Brown, who set out to study nursing before changing her major to education, said she kept talking to Grasso because she was fearful her friend might lose consciousness.

Grasso’s mother called Brown, who graduated from Deering High School, a hero.

“Sabina was knocked out cold,” said her mother, Terri Grasso of Cumberland Foreside. “She suffered a severe blow to the head.”

Grasso is scheduled to see a neurologist this week in Portland, but her mother says her daughter is struggling. She won’t be able to return to school this week. Grasso is a junior at Endicott College in the Boston area.

“Something clearly hit her,” said Terri Grasso, who is hoping that TD Garden will provide her with an explanation of what happened. She stopped short of specifying what type of object hit her daughter.

Tricia McCorkle, a spokeswoman for TD Garden, said in an email Sunday night that the investigation is continuing.

TD Garden issued the following statement after the accident: “Two fans were injured following last night’s Bruins game when a safety net fell unexpectedly. Our immediate concern is the well-being of these two fans. Safety of our fans is our top priority and we are investigating the incident.”

McCorkle, who was contacted by telephone and email, had no further comment.

Brown and Grasso had never been to a Bruins game before. but McDonough, 20, who played for Cheverus High School’s girls’ hockey team, enjoys the sport.

Grasso and McDonough graduated from Cheverus in 2011.

McDonough’s father, who grew up Woburn, Mass., said he received a phone call Saturday from Boston Bruins President Cam Neely inquiring about his daughter’s well-being.

McDonough said he was impressed that Neely made the effort to reach out to him, but he still would like some answers.

“He is a genuine, sincere individual who seems to be concerned about everyone’s safety. That was very much appreciated,” McDonough said.

Neely told him that he does not know how the accident happened. “They were out having a good time,” McDonough said of his daughter and her friends. “It should have been a safe environment for them.”

Dennis Hoey can be contacted at 791-6365 or at:dhoey@pressherald.com