Ms. Lundquist did not like to eat in the dining hall, so Mrs. Barrow would take her own meals in their room to keep her company, Mr. Barrow said.

In court papers, lawyers for Brandon Woods cited those meals as evidence that the two women “generally carried on a caring friendship.”

In January 2009, court records show, workers at the nursing home reported that at times Ms. Lundquist “became jealous of her roommate, who she perceived sometimes got extra attention.”

Her agitation, the records show, grew when Mrs. Barrow had visitors. Ms. Lundquist also accused Mrs. Barrow of having “too many flowers and of taking her belongings,” according to records made by workers at the home just a month before the death.

Knowing that his mother was not one “to rock the boat,” Mr. Barrow said he asked a member of the nursing staff whether she should get a new roommate. The staff member did not seem to think there was a problem, he said.

On Aug. 21, Mrs. Barrow turned 100. Her son and three grandchildren took her on a shopping trip to Walmart. They ate cake with green frosting, and she declared it her goal to live to 104.

A month later, back at the nursing home, a simple disagreement between the roommates escalated.

It began when Mrs. Barrow asked a nursing assistant to move a table from the foot of Ms. Lundquist’s bed so that she could get to the bathroom. At that request, Ms. Lundquist got out of bed, screamed, “was verbally abusive and hit” the nursing assistant, records show. It took two staff members to calm Ms. Lundquist.