A 19-year-old Brockton woman died Saturday after she was struck while crossing the street in a busy shopping area in Avon, according to a spokesman for Norfolk District Attorney Michael W. Morrissey.

Ariel Dineen was on an afternoon break from her job at Party City and crossing Stockwell Drive, walking west toward a Dunkin’ Donuts, where her sister works, according to David Traub, the spokesman.

She had crossed both northbound lanes, walked over the median, and had made it into the second southbound lane when she was struck by a Jeep, Traub said.

Dineen’s death is under investigation, he said.

Relatives who spoke to a reporter Sunday said Dineen’s family is not ready to comment.

She was a 2015 graduate of Southeastern Regional Vocational Technical High School in South Easton, where she played on the volleyball team, according to Luis G. Lopes, superintendent of the school district.

“She was a very outgoing member of our school community,’’ Lopes said in an e-mail. “Ariel always stood up for what she believed in and was loved by her peers and the faculty at our school.’’

Lopes said the school would have grief counselors available to students and staff on Monday, “and we have already reached out to some of her teachers and friends to offer our condolences and support.’’

Krystina O’Sullivan, 18, said she met Dineen about a year ago, when both were working at Party City for the busy Halloween shopping season.

“When we met, we instantly hit it off and became friends,’’ O’Sullivan said in a Facebook message to a reporter. “She always had the ability to make anybody smile and had the best personality.’’

O’Sullivan, a Roslindale native attending Unity College in Maine, recalled that one day she had walked into the store in tears because she and a boyfriend had broken up. Dineen left the aisle where she was working and wiped the tears from O’Sullivan’s face, she said, then worked to cheer her up.

“She was most definitely always there for any single one of her friends,’’ O’Sullivan said.

Jeremy C. Fox can be reached at jeremy.fox@globe.com. Follow him on Twitter @jeremycfox.