Since their marriage in 1931, Thomas May had doted on his wife Lilian. But the woman he wed was not the woman who failed to recognize half her relatives at their 55th anniversary party 10 days ago and who needed her husband to cook for her, wash her clothes, help her dress and bathe.

Thomas May was not the same man either. For about five years he had watched his small, white-haired wife succumb to Alzheimer's disease, an irreversible disintegration of the brain that causes people to become increasingly senile. He cared for her as she became more disoriented, yet told friends the pressure was becoming too much to bear. And Wednesday night he shot and killed his wife, and then he shot and killed himself, according to police.

About 9 p.m. Wednesday, Thomas May, 80, called his niece in Baltimore to tell her that "he couldn't stand the pressure any longer," said Anne Arundel County police spokesman V. Thomas Molloy. "It really got to him, and he couldn't see her like that any more. He said that he had shot her and he was going to shoot himself . . . The niece tried to talk to him for about 15 minutes, but he was determined."

Molloy said that when May telephoned his niece, Irene Duvall, to tell her what he had done, he added that he had sorted out personal papers and bank records.

Molloy said Duvall tried to dissuade her uncle but he suddenly hung up on her.

Duvall called her son, who telephoned police. When three police officers arrived at the house about 9:30 p.m., Molloy said, they found Lilian May lying on a bed with a bullet through her heart, and her husband in another room with a .38-caliber handgun and a bullet in his head.

According to neighbors, Lilian May, who was in her seventies, was physically fit but becoming increasingly disoriented, and was often incoherent. Sometimes she could put on her own shoes, and sometimes she would forget she was already dressed and put on three dresses on top of each other. But her husband told friends that he was determined to look after her himself and vowed he would never abandon her to the care of others.

"Every time he'd come over here and talk, he'd say it was getting worse and worse, and that he was becoming very despondent," said Edward P. Macknovitz, a neighbor for 28 years. "He was much better physically and mentally than she was. I think that her condition just wore him down." Yet he never asked for help and the couple had no children to turn to, according to Macknovitz.

Alzheimer's disease affects an estimated 2.5 million adults, primarily those over 65. Although it leaves its victims physically healthy, the degenerative disease can cause memory loss, confusion, difficulty in speech and movement and inability to recognize friends and family members.

Marilyn Benson, a volunteer with the Washington area Alzheimer's Disease Association who cared for her husband as he suffered from the illness for seven years before dying last year, said murder and suicide are thoughts that occur frequently as spouses try to care for Alzheimer's disease victims. Spouses frequently forget to care for their own physical and mental health as they struggle to cope with the long-lasting disease, she added.

Although he would not let others care for his wife, Thomas May allowed two neighbors to help him clean house every other Tuesday. One of the two women, Cecelia Gatton, said Thomas May had seemed depressed during the winter but had become more cheerful with the warmer weather.

He would take his wife, whom he called Lil, out for walks in the garden where he would feed squirrels and chipmunks and tend his flowers.

Just a couple of weeks ago, Gatton said, he had put up fences to protect his geraniums from rabbits.

May, a retired engineer for Baltimore Gas & Electric, would take his wife on day trips, she said, often into Washington.

When she last saw him the day before he killed his wife and himself, she said, he was talking of taking his wife on a trip to Busch Gardens near Williamsburg.

"He took very good care of her," Gatton said. "He was devoted to her. It's so hard to believe that he was capable of doing anything to her, but he must have reached his limit, and something snapped.

"He would call her 'Lil' or 'Sweetie.' He was just so gentle and loving it was hard to describe -- she was just so precious to him," Gatton said. "He was very protective of her, and just very loving. And I guess he acted out of love."

Staff writer Joseph E. Bouchard contributed to this report.