Pakistani and American police hunting the terrorists who assassinated two US diplomats in Karachi are investigating the possiblity that the murder weapon was used before - against worshippers at a mosque and in the massacre of a family in which the killers first ate their victims' supper.
Nearly 50 forensic experts and detectives from the FBI are assisting Pakistani police in tracking down the diplomats' killers in Karachi, a city of 12 million submerged in a state of near anarchy. Authorities have lost control of the city to rival gangs who kill nearly a dozen people a day in ethnic and religious feuds.
Even with a reward of $2m (£1.2m) offered by the Clinton administration, the FBI faces an impossible task. Many Karachi neighbourhoods are "no- go" areas for the local police. An American policeman is even more at risk.
Despite these dangers, investigators are reportedly close to identifying the two assassins who hijacked a taxi, pulled up alongside an American embassy van at a red light on the main airport road on 8 March, and sprayed the passengers with small arms fire from AK-47 assault rifles, killing Gary Durell and Jackie van Landingham, and injuring a third diplomat.
Using ballistic tests, the FBI was reportedly able to match one of the weapons used to an incident on 25 February when gunmen, believed to be Sunni Muslim extremists, fired upon Shia worshippers as they were kneeling for prayers in the open courtyard of a mosque. Fourteen people were killed.
The same gun appeared in a macabre slaughter this month when gunmen broke into a Shia household, locked up the women and calmly helped themselves to dinner. They then lined up seven men and, one by one, killed each man with a bullet through the eye. This massacre shocked even Karachi's citizens, already reeling from more than 300 murders this year.
The list of organisations which would want to kill US diplomats is long and messy. To complicate the mystery, it appears that Ms Landingham, described as a secretary at the Karachi consulate, and Mr Durell, a technician, may have been working under cover for the Central Intelligence Agency (CIA). Neither diplomat was registered as required with the Pakistani foreign office as belonging to the US embassy staff in Karachi.
The CIA is searching in Pakistan for clues to the bombing of the Trade Center bombing in New York in 1993. A man described by police as the ringleader, Ramzi Yousef, 27, was arrested recently in Islamabad. Pakistani police captured six of his alleged accomplices this month.
Pakistani and US investigators are considering whether the diplomats may have been killed in revenge for Yousef's extradition. Another theory is that the pair were killed to sabotage a trip by Benazir Bhutto, the Pakistani Prime Minister, to Washington on 5 April. But the reverse seems to have happened: Ms Bhutto has used their murder to seek US aid in combating "extremist terrorism".
Many Karachi citizens are resentful, however, that only now, after the murder of the two Americans, is Ms Bhutto trying to restore order in Karachi. Anwar Kazmi, a social worker who goes out in ambulances to collect the dead and wounded from Karachi's streets, said, "Over a thousand people were in killed in Karachi this last year. What about us? Why does Benazir only care about the two Americans?"