A 71-year-old woman looking to sit on a crowded Red Line train at Harvard Square during the evening commute was allegedly punched in the head by a younger woman who angrily refused to free up a seat by moving her pocketbook, according to Transit Police.

The incident played out Friday about 5 p.m., as the older woman boarded a train that Transit Police described as crowded, with all seats taken and some passengers standing. The alleged victim noticed that the younger woman, later identified as Jada Campbell, put her pocketbook on an otherwise vacant seat.

“The victim politely asked Campbell to hold her purse so the seat could free up and the victim could sit down. Campbell refused to do so,’’ Transit Police wrote. “The victim then handed the purse to Campbell and was about to take a seat. Campbell became enraged and physically threatened to harm the victim.”


The older woman moved away from 23-year-old Campbell, who allegedly punched the older woman in the back of her head.

Transit Police arrived and arrested Campbell for assault and battery on a person over 60 years old, resisting arrest, and intimidation of a witness, Transit Police wrote. “Campbell threatened victim/witnesses for speaking” with police.

John R. Ellement can be reached at ellement@globe.com. Follow him on Twitter @JREbosglobe.