Lahore Police chief Aslam Tareen described the killing of the two men by Davis in the city on January 27 as an act of "cold-blooded murder".
Though Davis initially said he had acted in self-defence, he remained silent throughout the investigation and did not offer anything to support his claim, Tareen said.
"We have proved that it was not a case of self-defence, it was a clear-cut murder," Tareen told a news conference shortly after a judicial magistrate''s court in Lahore ordered Davis to be sent to prison for a fortnight.
An interim ''challan'' or chargesheet with a murder charge under Section 302 of the Pakistan Penal Code had been submitted against Davis, Tareen said.
The report was finalised after police completed the investigation and received several forensic reports.
"Some more reports are awaited, and the final challan will be submitted once we get them," he said.
Davis was arrested after he gunned down the two armed men in a busy area of Lahore last month. A third Pakistani was killed when he was hit by a US consulate car rushing to help Davis.
Asked why police had rejected Davis' plea of self-defence, Tareen replied: "That had been considered but the eyewitnesses, the other witnesses and the forensic reports, they showed that it was not a case of self-defence.
"His self-defence plea was considered and keeping in view the witnesses and the forensic (reports), that has been rejected by the investigators," he said.
The killing of the two men was an "intentional" act and they were "murdered", Tareen said.
Davis fired 10 bullets at the two men and eyewitnesses said he shot one of them while he was trying to run away, the police chief added.
"It means that he (Davis) has ensured that they will be killed. They had not been given any chance to survive or (to) be arrested or whatever it is. So that's why we cannot take it as self-defence," he said.
Though Davis had said that one of the men cocked his pistol and pointed it at him, Tareen said forensic tests had shown that there was no bullet in the chamber as it was not cocked.
"So neither it has been cocked nor it has been pointed at Raymond," he said.
Tareen said police still had not been given access by US authorities to the car and officials involved in the death of the third Pakistani.
Five reminders had been sent to American officials in this regard.
"Once we get access to them, we will finalise the case and send it to court," he said.
The police chief refused to comment on the reasons or motive for the killings.
He also said it was up to the federal government to decide whether Davis enjoys diplomatic immunity.
The murder charge against Davis will further complicate the stand-off between Pakistan and the US over the official. The case has already taken the already tense relationship between the two countries to a new low.
The US has suspended all high-level contacts with Pakistan and reports have suggested they will not be resumed till Davis is freed.
US lawmakers have warned that the matter could affect American civil and military aid running into billions of dollars.
There are also reports that the matter could impact an upcoming Pakistan-Afghanistan-US meeting and President Asif Ali Zardari''s visit to the US.
Top Pakistani leaders have rebuffed US demands for Davis to be freed on the ground that he enjoys diplomatic immunity, saying the matter will be decided in court according to the country''s laws.
Confusion also surrounds the identity of the two men killed by Davis.
Though the US official claimed they were robbers, some reports said they were operatives of the Inter-Services Intelligence agency who were assigned to track Davis.