By ELVA RAMIREZ and JONATHAN LEMIRE
An 87-year-old Brooklyn woman was brutally stabbed to death yesterday with a pair of scissors by her mentally disturbed granddaughter, whom cops found covered in blood, police said.

Alarmed by screams coming from the second-floor home on Ocean Ave., neighbors had called police shortly after 4 a.m.

Cops arrived to find Zoila Mosquera, 47, who had recently been hospitalized for mental illnesses, standing over the body of her grandmother, Cynthia Mosquera.

The victim was stabbed in her torso and face, a police source said.

"Leave me alone! Leave me alone! Don't bother me!'" Zoila Mosquera yelled at cops, according to Jamel Lane, 22, a UPS employee who lives directly below the Mosqueras.

Charges against Zoila Mosquera, who has one prior arrest for marijuana possession, were pending last night. Though police had no records of previous domestic disputes between her and her churchgoing grandmother, neighbors said the younger woman had been abusive previously.

"She almost killed her before," said neighbor Steve McCalla, 33, referring to a fight the women had about a decade ago.

Neighbors and police sources also said Zoila Mosquera - who frequently stopped taking her medication - had spent two weeks in a mental institution last June after claiming the FBI was following her.

"When she's on medication, she's a very nice person to speak to," McCalla said.

Cynthia Mosquera was a long-time parishioner of St. Mark's United Methodist Church. She got an award from the church in December for outstanding service to the community. She also was a frequent visitor to the church senior center, and would often go to arts and crafts classes with her granddaughter.

"We thought it was a fabulous relationship," said Theresa Coleman, 78, adding that she often saw the younger Mosquera kiss her grandma hello and carry her up the stairs of their home.