BRENTWOOD — Staff at the Hampton Inn in Brentwood found something unusual when collecting the linen of a recently vacated room: three pillow cases filled with stolen mail.

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One dead after double shooting at East Bay shopping center On Aug. 9, Brentwood police were called to the Hampton Inn at 7605 Brentwood Blvd. after the staff found drugs and the three pillow cases filled with suspected stolen mail from residents in the East Bay.

The police investigation found that suspects booked the hotel room online with fake names and used the hotel’s phone app and WiFi connection to access the room without a key. After the guests checked out, the pillow cases filled with mail were found. According to police, none of the mail was connected to Brentwood residents, but several articles of mail were addressed to Concord residents.

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The Hampton Inn in Brentwood uses the Hilton Honors Digital Key app that can be downloaded to either an iPhone or Android phone and lets the user unlock a room without checking in or out at the front desk.

Since the Digital Key technology was rolled out at Hilton hotels in 2015, it has expanded to more than 1,000 hotels and looks to reach 2,500 by the end of 2017, according to a news release from the company. Guests have opened more than 6.4 million doors with their phones.

The case has been handed over to the U.S. Postal Inspector’s office in Oakland, which continues to investigate the incident and contact all the victims for the mail that was recovered.

The U.S. Postal Inspection Service maintains a standing reward of $10,000 for any information that leads to the arrest of suspects in mail theft cases. Mail theft is a misdemeanor in California, but is a felony to the federal government and carries with it a sentence of up to five years in federal prison and a $250,000 fine.

Anyone with more information on this case can call the US Postal Inspector’s 24-hour number at 1-877-876-2455.