Washington ? Targeted college campus violence, from serious assaults to the mass shootings at Virginia Tech in 2007, is up sharply over the last two decades.

The number of cases rose from 40 during the 1980s to 79 in the 1990s and 83 since 2000, says a study issued Friday by the FBI, Secret Service and Education Department.

The cause of the increase is unknown, though the report noted a dramatic rise in college student enrollment in the past 20 years.

“For years, colleges and universities have worked to address this challenge — to create safe campuses where academic and personal growth can flourish,” says the study, “Campus Attacks.” “In the wake of the Virginia Tech tragedy, many universities were confronted with the troubling reality that one person can, in a few brief moments, devastate a college community through an act of targeted violence.”

The report was released on the third anniversary of the shooting rampage by Virginia Tech student Seung-Hui Cho, who killed 32 students and faculty members and took his own life. The report comes as a result of recommendations from a federal panel that studied that tragedy.

In the 272 incidents of targeted violence studied for the report, 281 people were killed 247 injured. Of those deaths, at least 190 were students and at least 72 were employees.

Targeted violence is defined as cases where attackers select a victim beforehand or randomly choose victims because they fit some predetermined profile or relationship. It excludes violence that breaks out spontaneously, such as during an argument.

The study found that:

• Factors relating to an intimate relationship were a motivating or triggering factor in a third of attacks and academic stress or failure was a factor in one out of 10 attacks.

• Sixty percent of those who engaged in targeted campus violence were current or former students at the school where the violence took place.

• Firearms were used in more than half the incidents and knives or weapons with a blade were used in over 20 percent.

• Over 90 percent of those who committed such attacks were male.