An alert police officer and a tip led to the arrest of two men accused of beating a senior citizen and her 40-year-old caretaker Thursday morning in Waialae Nui.

Prosecutors yesterday charged Zachary Robinson, 19, and Cody Mikami, 21, with first-degree attempted murder, two counts of second-degree attempted murder and first-degree robbery in the case. Bail has been set for both men at $1 million.

Robinson and Mikami are scheduled to appear in District Court tomorrow.

The men are accused of beating 85-year-old Mary Lee Koskinen and 40-year-old Matthew Edmondson in their home about 3:30 a.m. Thursday in a home invasion robbery. Koskinen and Edmondson were both taken to the hospital in critical condition, police said.

According to court documents, police responded to the home at 1451 Halekoa Drive at 3:26 a.m. and found Koskinen on her back in extreme pain and Edmondson in the living room with his face covered in blood.

He had two black eyes and multiple lacerations on his face. Next to him was a brick and tire iron apparently covered in blood.

The officers also found two bags containing computer equipment nearby.

Police said the victims were too severely injured to give a statement.

A neighbor reported seeing a strange man standing in her garage as police were conducting their investigation. A police officer noted the license plate numbers of vehicles in the area, including a black Toyota Tacoma pickup.

About seven hours later on Thursday, Anthony Chong, a plainclothes officer with the Waikiki Crime Reduction Unit, spotted Mikami driving a black Toyota pickup on McCully Street toward Waikiki.

Chong knew Mikami did not have a driver's license and followed him into a parking lot on McCully Street and Kalakaua Avenue.

Chong arrested Mikami for driving without a license and Robinson on two outstanding warrants.

Police eventually matched the license numbers at the home invasion scene with the truck Mikami was driving.

Police also received a tip on the case from an unidentified man.

The man said another man named “;Zach”; had asked him if he wanted to join the robbery, but he declined.

He said Zach had already been arrested and identified him in a photograph as Robinson.

The neighbor who saw a man standing in her garage also identified Robinson in a photograph.

Police arrested Robinson in connection with the home invasion Thursday night. Police said he was awaiting trial for a burglary in Waikiki in November and is a suspect in other burglaries.