"It could have been the perpetrators, but could also have been passers-by who got scared," said police spokesman Thomas Fuxborg.
The police have no formal suspects in the case which concerns three young victims who were shot dead.
A witness is reported to have seen the moped drive north from the scene near Uddevalla hospital around the time of the killings which were carried out between 1am and 1.30am on Saturday morning.
Police managed to identify the three victims on Saturday and have reported that there are two men, born 1992 and 1993, and one woman, born 1996. All are residents of Uddevalla.
Thomas Fuxborg confirmed that the victims had been shot but declined to confirm how many shots had been fired. There are currently no suspects and Fuxborg declined to comment on whether a motive had been established.
The bodies were found by a jogger at around 7am on Saturday morning. The jogger found a dead man in a car and when the police arrived two further bodies were found lying nearby.
The area around the suspected murders remained cordoned off on Saturday afternoon and large numbers of residents and mourners gathered at the hospital in the course of the day. Ambulance staff worked hard to offer help and support to the crowd, which at times became agitated.
Police were obliged to intervene at one stage to prevent a group of 20 people from forcing their way through the cordon to the scene.
The emergency services were backed up by municipal crisis counsellors.
"We can help by being on hand, consoling, trying to calm people down and sharing out blankets," said local Church of Sweden pastor Ingvar Humlén.
Many residents of Uddevalla, home to around 30,000 people, expressed shock over the gruesome events.