To speak frankly, and, I think for all of us ...
First of all, sorry for your loss of a friend. Many of us have lost friends to drugs in various ways, I know I have, so our sympathies go out.
However it's important to gather as much information about cases like this as possible not just out of a morbid curiosity but to learn more about the drugs and the attendant risks. As far as DPT goes knowing what we know about this drug, absent any real and in depth forensic toxicology, it's hearsay. It's a shame for a young kid to pass this way, but implicating this particular drug seems like a pretty remote possibility.
Arguably equally hearsay sources on Erowid &c., after a brief perusal, report survival at doses in excess of 100mg, i.m., and tachycardia and an ER visit at 50mg, insufflated. No fatalities.
Nobody is saying that it is impossible that DPT killed this kid. But given the fact that this drug has been out for quite some time and we do not hear a lot, or at all, about related fatalities makes us skeptical. The mention of other "mysterious" psychedelics and stimulants compounds our skepticism as any number of these are more likely to be fatal than DPT. But perhaps if we are talking about a truly heroic dose or an idiosyncratic reaction (or a pre-existing medical condition, say, Wolff-Parkinson-White or really any number of things), then maybe DPT alone could account for a fatality. But rumours in a high school, grieving parents, and media histrionics about "mysterious drugs" and DPT believe to have killed him do not make for very reliable evidence of this.
We would all love to see some concrete data, but unfortunately we probably will not. What we would really like to know is how DPT came to be named and implicated in this case. Was a full forensic workup done? Was a bag labelled/analyzed as "DPT" found on his person? Mislabeling of these drugs has been known to occur from time to time with regrettable and at times fatal results, so if that's all it is it is a case of jumping to conclusions. Unfortunately the media does not do a very good job of reporting in cases like this nor do they have a lot of incentive to as their target audiences don't much care for the intricacies of regular "street" drugs, let alone exotic things like DPT.
Edited to add: Someone is editing Wikipedia to reference this incident, and I don't know their policies but I don't think that what we have here qualifies as a reliable source.