This guy seems a little "off," as I've worked with everybody from US Marshals Office / USCS down to local Sheriff's deparment, and I have yet to see anyone who carried that much stuff let alone felt they needed to. One particular USCS supervisor (now retired) with whom I've worked simply carried a S&W 659 in a shoulder holster w/ 4 spare mags and a sharp folding knife and this guy was heavily involved in the drug war against Pablo Escobar, back in the day.
Interestingly, if this guy is DEA, I certainly don't recognize that badge as being DEA issue. Perhaps he's a "lone operator" who needs all that stuff.
Anyway, Federal law enforcement, much like state and local law enforcement typically don't work alone, nor even in pairs especially on things such as investigation of drug trafficking, etc. They work in TEAMS--large groups of people, often times a dozen or more.
I've seen primary guns, backup guns, perhaps one fixed blade and one small folder for small chores, and of course shotguns and rifles in the trunks of cars until needed. Chances are this guy will never get the opportunity to use all that stuff. 'Nuff said.
As for carrying a pager and a cell phone that is NOT at all uncommon. Most agencies issue pagers particularly to Detectives, Investigators, Special Agents and the like. Mobile phones are typically personally owned and paid for as the dept./agency does not have the funding. Strange, where is his two-way radio? Perhaps its back at his office.