New developments in Falcon Lake death

ZAPATA COUNTY, Texas (NBC) - In David Hartley's last hours, a video shows him behind the wheel of his truck, pulling the couple's Jet Skis as they headed to Falcon Lake.

Just a short time later, his wife, Tiffany, said they came under a barrage of gunfire while Jet Skiing. She said David was shot in the head on the Mexico side of the waterway.

On police dashcam video, Hartley can be heard talking with Texas Department of Public Safety troopers - who stopped him for an expired registration sticker.

• Trooper: "Where you headed to?"
• Hartley: "Up to Falcon."
• Trooper: "To Falcon?"
• Hartley: "Yes."
• Trooper: "How long were you going to stay up there?"
• Hartley: "At Falcon? Just for the day."
• Trooper: "Just for the day?"
• Hartley: "Yeah."

Meanwhile, it was widely reported throughout the weekend that mexican police had identified two suspects, brothers, connected to the Zeta drug cartel.

However, Mexican officials dismissed those reports to a Texas newspaper late Sunday night. U.S. authorities are puzzled as well.

"We are trying to find out how this information came about," said Zapata County Sheriff Sigifredo Gonzalez.

Tiffany is still frustrated by the scope and pace of Mexico's search for David.

"Until we get some more footage and video or, you know, pictures to say this is what they're doing, you know, we're just hoping and praying that they're doing what they say they're doing," said Tiffany.

Tiffany gave NBC News an exclusive look at evidence authorities have analyzed, including her Jet Ski - the one she raced back to the U.S. side of the lake.

Also part of the evidence analyzed was her life vest - the one the Zapata County sheriff said contains microscopic stains, believed to be David's blood that splattered on Tiffany when she tried to help him.

Looking back on a marriage filled with adventure, Tiffany said she wonders whether that passion for excitement may have cost David his life.

For all who loved him, there is so much grief and still no closure.

"You hear this, you hear that. You don't know what's true. You don't know what to believe," said Pam Hartley, David's mother. "But I'm not giving up hope that we are going to find him and that we are going to bring him home. So everything we do get, it's ... I hope. It's always hope."