Murder-suicide: Information from Answers.com

Suicide to facilitate murder, as in suicide bombing
Murder to facilitate suicide, such as driving a car of four off a bridge.
Suicide after murder to escape punishment
Suicide after murder as a form of self-punishment
Joint suicide in the form of killing the other with consent, and then killing oneself

Many spree killings have ended in suicide, such as in many school shootings. Some cases of cult suicide may also involve murder.

Homicide and suicide

Ajax, son of Telamon , preparing suicide. Reproduction from a black-figure amphora depiction by Exekias (550-525 BC).

According to the psychiatrist Karl A. Menninger, murder and suicide are interchangeable acts - suicide sometimes forestalling murder, and vice versa.^[1] Following Freudian logic, severe repression of natural instincts due to early childhood abuse, may lead the death instinct to emerge in a twisted form. The cultural anthropologist Ernest Becker, whose theories on the human notion of death is strongly influenced by Freud, views the fear of death as a universal phenomenon, a fear repressed in the unconscious and of which people are largely unaware. This fear can move individuals toward heroism, but also to scapegoating. Failed attempts to achieve heroism, according to this view, can lead to mental illness and/or antisocial behavior.^[2]

In a research specifically related to murder-suicide, Milton Rosenbaum (1990) discovered the murder-suicide perpetrators to be vastly different from perpetrators of homicide alone. Whereas murderer-suicides were found to be highly depressed and overwhelmingly men, other murderers were not generally depressed and more likely to include women in their ranks.^[3] In the U.S. the overwhelming number of cases are male-on-female and involve guns. Around one-third of partner homicides end in the suicide of the perpetrator. From national and international data and interviews with family members of murder-suicide perpetrators, the following are the key predictors of murder-suicide:access to a gun, a history of substance abuse, the male partner some years older than the female partner, a break-up or pending break-up, a history of battering, suicidal ideation by the perpetrator.

Though there's no national tracking system for murder-suicides in the United States, medical studies into the phenomenon estimate between 1,000 to 1,500 deaths per year in the US ^[4], with the majority occurring between spouses or intimate partners, males were the vast majority of the perpetrators, and over 90% of murder suicides involved a firearm. Depression, financial problems, and other problems are generally motivators.